Listings show a variety of overall dimensions across different products. Example measurements from the results include: "2 inches (H) x 12 inches (W) x 17 inches (D)", "3 inches (H) x 13 inches (W) x 16 inches (D)", "15 inches (H) x 7 inches (W) x 7 inches (D)", and "16 inches (H) x 12 inches (W) x 5 inches (D)". Other listings show similar measurements in the product details.
Capacity varies by listing. Examples from the results include 18 liters, 16 liters, 14.86 liters, and 30 liters, indicating a range of small to larger backpack capacities depending on the model.
Many mermaid backpacks include a roomy main compartment plus a smaller front zip pocket and side mesh pockets for bottles. Some listings note multiple interior compartments or additional pockets, while at least one listing specifies no compartments or pockets.
Most listings describe padded, adjustable shoulder straps and a top carry/hang loop. A few listings also mention a cushioned back panel for added comfort.
Some listings are sold as sets that include an insulated lunch box or a detachable lunch tote attached to the backpack. Other sets may include accessories such as a clear gadget case and a carabiner.
Most listings show a zip closure for the main compartment (often described as a "main zipper compartment"). At least one listing lists the main compartment as "Open, No Closure."
